In recent years, in electric vehicles (EVs) and hybrid electric vehicles (HEVs), there is demand for electric motors that improve riding comfort by reducing electromagnetic vibrational forces, and that can also operate up to high-speed regions.
In consideration of such conditions, electric motors have been proposed in which electromagnetic vibrational force reducing grooves are formed on a surface of a rotor core so as to be positioned around an outer circumference of permanent magnets (see Patent Literature 1, for example).
In the electric motor that is described in Patent Literature 1, it is claimed that electromagnetic vibrational forces can be reduced by appropriately selecting a groove width of the electromagnetic vibrational force reducing grooves relative to a slit pitch and a slit width of the stator core, enabling noise to be reduced.